This invention pertains to the field of oil refining and the petrochemical industry, and more particularly to installations for the vacuum distillation of liquids, such as crude oil for instance. The invention can be used for the rectification of an oil stock. Additionally, the invention relates to the field of environmental protection from pestiferous industrial waste since there is no discharge of water-oil emulsion, which is an ordinary oil refining waste, when the invention is used for the rectification of oil.
An installation for the distillation of crude oil is known, which has a vacuum rectification column and a steam ejector maintaining a reduced pressure in the column (see U.S. Pat. No. 2,680,709, cl. 202-204, 1954).
Water condensate contaminated with oil products is generated during operation of this installation. Such water condensate has to pass special depuration before it is discharged into industrial drainage. Depuration of the wastewater containing water-oil emulsion (mixture of steam condensate and liquid hydrocarbons) is very expensive. At the present time, there are not any sufficiently inexpensive and productive means for effective depuration of the waste water of oil refineries.
A plant for distilling liquid products disclosed in RU patent No. 2048156, M cl., B OI D Mar. 10, 1995, has been chosen as the starting point for the invention. The plant has a vacuum rectification column with pipes for feed of a stock product and for bleeding of a gas-vapor phase and a liquid fraction. Further, the plant has a vacuum-producing device composed of a liquid-gas jet apparatus, a separator and a pump.
During operation of the RU ""156 plant the gas-vapor phase is evacuated from the rectification column by the liquid-gas jet apparatus. The liquid fraction from the rectification column is used as an active medium for the liquid-gas jet apparatus. Such provides a reduced negative environmental discharge of waste substances (water-oil emulsion).
One imperfection of the RU ""156 plant is the unstable operation of the separator conducing to recurring emission of gases and to consequential loss in the base product output. Said emissions of the gaseous phase from the separator take place due to incomplete condensation of the gas-vapor phase during its mixing with the active liquid in the jet apparatus. These emissions disturb the dynamic balance between the elements of the vacuum system and result in periodic overloading of the separator.
The objective of the present invention is to increase the efficiency of the distillation plant and to increase output of the base products due to complete condensation of easy-condensable components of the gas-vapor phase during mixing of the gas-vapor phase with the active liquid in the jet apparatus. This allows one to reduce loading of the separator, to make the operation of the separator more stable and to prevent the emission of the non-condensed components of the gaseous phase.
The stated objective is achieved because the vacuum-producing device composed of a liquid-gas jet apparatus, a separator and a pump, which is a part of the distillation plant having the vacuum-producing device and a vacuum rectification column with pipes for feed of a stock product, and for bleed of a gas-vapor phase and at least one liquid fraction, is furnished with a condenser. The gas intake of the liquid-gas jet apparatus communicates with the pipeline for bleed of a gas-vapor phase, the liquid intake of the liquid-gas jet apparatus is connected to the discharge side of the pump and the outlet of the liquid-gas jet apparatus is connected to the condenser""s intake. The intake of the separator is connected to the condenser""s outlet, the liquid outlet of the separator is connected to the suction side of the pump and the gas outlet of the separator is connected to consumers of compressed gas. There is a variant of the plant wherein the condenser has an additional liquid intake, which is connected to the discharge side of the pump. Another variant is when the condenser is connected to the pipeline for bleed of a liquid fraction from the rectification column.
In all of the introduced variants of the plant, it is preferable to connect the pipeline for bleeding of a liquid fraction to the suction side of the pump and to provide the condenser with a hydro seal.
When the condenser is placed upstream of the separator""s intake it is possible to arrange an adjustable and controlled process of condensation of easy-condensable components of the stock product in the active liquid medium of the jet apparatus. The specific location of the condenser in the vacuum-producing device has great significance. It is expedient to locate the condenser nearer to the separator when there is no additional supply of the active liquid into the condenser. This allows, on the one hand, a reduction of hydraulic losses in the pipeline between the jet apparatus and condenser because a liquid-gas mixture runs inside such pipeline, and, on the other hand, feeding of the separator by a more homogeneous medium with a lower content of the gaseous phase. In case there is a necessity to feed the condenser with an additional liquid medium in order to intensify condensation of easy-condensable components, it is expedient to locate the condenser nearer to the jet apparatus.
Either the liquid fraction from the rectification column or the active liquid from the discharge side of the pump can be used as the additional liquid for the condenser. Of the two, the most preferable is the liquid fraction from the rectification column. Input of the liquid fraction from the rectification column ensures renewal of the active liquid and stimulates condensation of easy-condensable components of the gas-vapor phase. Additionally, feed of the liquid fraction into the condenser reduces hydraulic losses during mixing with the active liquid and also provides for a more effective compression of non-condensable components of the gas-vapor phase. Consequently, pressure goes up in the manifold supplying compressed gas to consumers while energy consumption of the vacuum-producing device remains the same.
It is necessary to note that, besides more intensive gas separation, a decrease in pressure in the separator may cause the disturbance of a hydrodynamic balance between the condenser and the jet apparatus and deteriorated condensation of easy-condensable components in the active liquid. The availability of a hydro seal in the condenser hydraulically isolates the condenser and the separator. As a result, it is possible to extend the range of working pressures of the jet apparatus, condenser and separator, and to increase operational reliability and stability of the vacuum-producing device. All of this increases the efficiency of the distillation plant.